In cardiology image-controlled diagnostic or therapeutic inventions are often performed on the heart, for example catheter ablation, balloon dilation and the insertion of a stent. In ablation treatments the heart wall is selectively sclerosed at selected points in order to remove electrical short-circuit paths in the heart and tachycardias associated with them. In such interventions intracardial electrodes are generally first inserted into the heart, with which the heart is stimulated by an external pacemaker during the intervention. This is called “pacing” and serves to improve control of the activity of the heart during the intervention.
Such an intervention is usually performed using x-ray image control. Said x-ray images can for example be recorded using a C-arm x-ray device, it being possible for the image recording unit fixed to the C-arm to be swiveled around the patient at any angle, enabling realtime x-ray images, known as fluoroscopy images, to be recorded.
3D data records can also be recorded using a C-arm, with the C-arm rotating in what is known as a rotation pass through approximately 180° plus the fan angle of the C-arm around the patient and recording 50-500 projection images. These can be reconstructed to form a 3D data record.
Additionally an electroanatomical mapping system is also often used in a catheter ablation, one or more catheters being inserted into the relevant ventricle for the electrophysiological mapping of the heart wall. By mapping the heart wall with the electrodes a potential map of the heart wall is created. The exact determination of the position of the electrodes is performed for example with electromagnetic localization systems (for example with the CARTO® system from Biosense, Webster, Calif., USA). Here sensors are integrated into the medical instrument to detect electromagnetic field changes, while a electromagnetic field is constructed around the patient. In this way the position of the medical instrument can be determined.
Also known is intracardial or intravascular ultrasound imaging, in which an ultrasound head is introduced into a catheter tip.
It is additionally known in the prior art for a three-dimensional CT (computer tomography) or MR (magnetic resonance) data record to be acquired prior to an image-controlled intervention on the heart, e.g. for treating atrial flutter. This provides more anatomical details than the fluoroscopy images recorded during the intervention. These can therefore be superimposed with the anatomical 3D data record during the intervention, allowing the cardiologist to navigate using anatomical data in real time. Normally the 3D image data record is acquired 2-3 days before the actual intervention. As a result, significant imprecisions often arise, because e.g. the left atrium may change.
Another problem with imaging the heart in general is the motion of the beating heart. The problem can be solved by ECG triggering in many imaging procedures. In the case of a pre-operatively recorded 3D image data record it is important to trigger this in the same phase of motion of the heart, with the heart also being looked at during the intervention. This situation is complicated even further because patients often do not have a regular heartbeat.